Three test methods have been used.
Three standard test is a subjective test of immersion of a sample in water then manual peeling of the liners from the medium and a visual assessment of fibre tear. Absence of fibre tear indicates poor adhesive resistance to water damage.
The FEFCO method No. 9 involves the immersion of a piece of board in water with a specified number of glue bonds subjected to the load imposed by a hanging weight (either 250 or 350 g). The number of hours the bond can withstand the load is measured.
Another more objective method is described in Australian Pat. No. 581511. That patent discloses a technique of preparing a sample of corrugated board by isolating a portion of the outer liner by removing part of the liner to isolate one piece attached to the medium. A hole or eyelet is prepared in the other portion of the board and a plastic strip is hot melt bonded to the portion of liner to be tested.
Hooks are placed in a hole in the plastic strip and the board. The testing apparatus comprises a beam balance with a water collecter on one beam and the sample on the other. The plastic strip is connected to the balance beam while the paperboard sample is secured to the stand. Water is added progressively to the collecter until the wet sample fails and the liner is displaced from the medium. This method aims to apply a constantly increasing force parallel to the glue lines of the sample.
Whilst this test was the first method to produce quantitative results, a number of difficulties exist with this method. The apparatus is clumsy and difficult to control and must be attended by an operator. Sample preparation is tedious and must be carefully done to avoid damage to the medium. The wet sample also tends to tear at the hole in the second portion. Further, if the glue bond of the side to be tested is appreciably stronger than the glue bond in the other side of the sample, then failure occurs on the weaker side rather than on the side to be tested.